Electrical transformer



0er. 2, 192s. 1,685,946

A. G. ELLIS ELECTRICAL TRANSFORMER Filed May 19, 1923 l o 2| fymr" @M 16 i? '""A ali] 8 7 17 (El) a a s C s Cb S'EC d d d `e :gg-6

WITNESSES:

Patented Oct. 2, 1928. v

UNITED STATES PATENT oFFIcE.

,ALFRED GEORGE ELLIS, OF HALE, ENGLAND, ASSIGNOB TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMIANY, A CORPORATION OF PENNSYLVANIA.

ELECTRICAL TRANSFORMER.

Application led May 19, 1923, Serial No. 640,245, and in Great Britain June 20, 192%.

My invention relates to electrical trans' formers and has for its object to provide imlproved means for varying the ratio of transformation.

For this purpose it has heretofore been proposed for star-connected three-phase transformers to provide a rotatable switching device of the drum type within the cas-V ing of the transformer adapted to connect diiferent tappings from the transformer windings together to the neutral point.

In accordance with the present invention different ratios of transformation are obtainable by means of a regulating switch located inside the transformer casing and comprising a plurality of fixed contacts connected with t-he several tappings of a transformer winding and one or more movable contacts adapted to be moved over the fixed contacts by a combined rotational and translatory movement. Preferably a single movable contact is'provided for each phase winding, the whole being mounted on a shaft rotatable from the exterior of the transformer and having a screw-threadedI portion mounted in a nut secured to the transformer casing. Any other suitable means may however be employed to impart the desired rotational and translatory movement tothe movable contact or contacts. When tappings are taken from the neutral ends of the phase windings each movable contact may be adapted to engage each fixed contact of its respective phase in turn whereas when the tappin s are taken from intermediate points only o' the phase windings it may be adapted to bridge each pair of fixed contacts of its respective phase in turn.

In order that the invention may be more clearly understood and readily carried into practice reference will now be made to the accompanying drawings wherein Figs.v` l. and 2 represent by way lof example partly diagrammatic longitudinal sections through transformers equipped with regulating switches in accordance with the invention.

In each form illustrated the transformer is of the three-phase star connected type and comprises phase windings 3 located within a casing 4 in the usual manner, the regulating switch comprising three groups of fixed contacts 5 of any convenient type mounted on an insulating. support 6 within the transformer casing and a rotatable shaft 7 carrying three contact lingers 8 adapted to cooperate with the groups of contacts 5. 'lhe shaft 7 has a screwed portion 9 at one end and is mounted at opposite ends in a bushing 10 and nut 11 secured to the casing 4, one end projecting from the latter and carrying a hand-wheel 12 by which the shaft can be rotated.'

In the form illustrated by Fig. 1 the free ends 13 of the phase windingsy 3 are connected with separate line terminals not shown and tappings 14 from the neutral ends and intermediate points adjacent the neutral ends are connected with the groups of contacts 5. The contact fingers 8 are electrically connected by a metallic sleeve 15 which is insulated from the shaft 7 by an insulating sleeve 16, and thepitch of the screw is such that a single rotation of the hand-- wheel 12 moves each linger 8 from engagement with one fixed contact into engagement with the next adjacent contact of the same group. Consequently by sim ly rotating the hand-wheel 12 the ratio or transformation can be varied as desired within the limits imposed by the number and location of the tappings.

In the form illustrated by Fig. 2 the free ends of the phase windings 3 are connected with line terminals as before but the tappings 14 which are in this case indicated by the references a to e are taken from intermediate points only of the windings and are respectively connected with the terminals of the gro'ups 5 which are designated by like references, each tapping d being connected with two terminals as shown. The Contact fingers 8 are insulated from each other being mounted directly upon an insulating sleeve 16 and are adapted to bridge pairs of adjacent contacts of their respective groups 5, the arrangement being such that the ratio of transformation can be varied as desired in the same manner and withinthe same limits as before.

The several windings are so divided that the steps from a to I) and b to o are two and one-half percent of the whole Winding, and

the step from c to 0l and d to e are five percent of the whole winding.

The various stages in the connections are as follows: With thebrushes 8 making contact with the fingers o-d, the whole winding is in circuit. One complete rotation of the 'ill handle 12 in the counter-clockwise direction turns the brushes completely around and brings them into position to make contact with the fingers d-b in which position one section, namely the section from c to b, is cut out, that is to say, the two and one-half percent reduction is made in the windings. If now the handle is turned a number of times to bring the brushes 8 into position to make contact with the fingers arf-d, the two portions of the winding c-b, b-,a will be cut out and a five percent reduction made. If the handle is now rotated in the opposite direction, i. e. clockwise, a sufficient number of times to bring the brushes into the position @-6, the portions of the winding e to d and c to b are cut out, that is to say seven and one-half percent of the whole. Finally the handle is rotated to bring the brushes into position to make contact with the fingers e-a in which the whole of the sections are cut out, that is to say ten percent of the winding is eliminated. rlhe sequence of positions is therefore o-d, d-b, w-rl, b-e and finally e-a.

In each construction a suitable indicating device 17 may be provided outside the transformer casing to indicate the positions to which the hand-wheel or equivalent should be turned to eect the several connections.

The invention is not limited to three-phase transformers but is obviously applicable to single phase and poly-phase star-connected transformers, while the form of apparatus illustrated by Fig. 2 of the drawings is also applicable to delta connected three-phase transformers.

Although I have described a specific embodiment of my invention, it will be obvious to those skilled in the art that various modifications may be made in the details of construction and arrangement of parts without departing from the principles herein set forth. I desire, therefore, to be limited only to the spirit and scope of my invention, as set forth in the appended claims.

I claim as my invention:

1. In a. transformer structure, a casing, a plurality of windings therein, a plurality of stationary contact members connected to said windings, a shaft mounted in said c'asing, means for longitudinally moving sa'id shaft at uniform speed during rotation thereof, and contact members mounted on saidy said shaft for engagement with said stationary contact members, said shaft and its contact members constituting a neutral point in the connection of said windings.

. 3. In a transformer structure, a casing, a threaded member mounted thereon, a plurality of windings in said casing, a plurality of stationary contact members connected to said windings, a threaded shaft mounted in said threaded member and adapted for rotational and longitudinal movement in said casing, and contact members mounted on said shaft for engagement with said stationary contact members.

4. In a transformer structure, a casing, a threaded member mounted thereon, a plurality of. windings in said casing, a plurality of stationary contact members connected to said windings, a threaded shaft mounted in said threaded member and adapted for rotational and longitudinal movement in said casing, and contact members mounted on said shaft for engagement with said stationary Contact members, said shaft and its contact members constituting a neutral point in the connection of said windings.

In testimony whereof, I have hereunto subscribed my name this second day of May,

ALFRED GEORGE ELLIS. 

